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make_array null handling with nested version #7136
Description
Is your feature request related to a problem or challenge?
Follow up on #6900. Implement array() nested version.
It seems calling array() for list return flattened list according to the comment
However, I think make_array should wrap the elements into array, the expected behavior
make_array([A,X], []) -> [[A,X], []],
make_array([null, Y], [Q,R,S]) -> [[null,Y],[Q,R,S]] and
make_array([C,Z], null) -> [[C,Z], null]
Main branch:
query ?
select make_array(['A','X'], []);
----
[[A, X], ]
query ?
select make_array(make_array(null,'Y'), make_array('Q','R','S'));
----
[[, Y], [Q, R, S]]
query error DataFusion error: Optimizer rule 'simplify_expressions' failed
caused by
Internal error: failed to downcast\. This was likely caused by a bug in DataFusion's code and we would welcome that you file an bug report in our issue tracker
select make_array(['C','Z'], null);
As a result, only the third case fails, the first case is acceptable but should we expected [[A, X], []] to differentiate with null can also be discussed
Describe the solution you'd like
Fix the third case and update the comments.
Optional: Expect the first case to return [[A, X], []]
Describe alternatives you've considered
No response
Additional context
No response
Activity
jayzhan211 commentedon Jul 30, 2023
@alamb @izveigor Request your comment on this issue, thank you!
jayzhan211 commentedon Jul 30, 2023
Duckdb result
alamb commentedon Jul 30, 2023
My suggestion is to follow the DuckDB / Clickhouse behavior
We are having a similar discussion about semantics of Unnest here #7088 (comment)
Maybe @vincev has some opinions as well
vincev commentedon Jul 30, 2023
This makes sense to me too, another thing I have noticed (maybe related to this) is that arrays with a null value generate error:
DuckDB generates:
vincev commentedon Jul 30, 2023
Oh I see there is a workaround for that:
izveigor commentedon Jul 30, 2023
Agree with @alamb and @vincev. Thank you for bringing this topic up, @jayzhan211.
I have created a separate ticket for handling
NULLand empty arrays: #7143.jayzhan211 commentedon Jul 31, 2023
I will fix the third case first.